Composition and method for stabilizing road base

ABSTRACT

A mixture, comprising of fly ash and an emulsion, where said emulsion is mixed with said fly ash in a range of 5% to 50% of fly ash per an area of a square yard and 0.5 gallons to 2.5 gallons per square yard of the emulsion to said area.

The present application claims domestic priority to provisionalapplication U.S.60/588,935, titled “Composition and Method forStabilizing Road Base,” filed Jul. 16, 2004, the entire contents ofwhich are incorporated herein by reference for all purposes.

FIELD

The present disclosure relates to stabilizers of roadways using acombination of combustion products and emulsions. However, there may beother uses of the disclosed products, such as dust suppressants, soilstabilizers, etc.

BACKGROUND AND SUMMARY

Every year, significant quantities of combustion products, includingcoal combustion products, are produced, including various types of ash,such as bottom ash, boiler slag and fly ash. These products areconsidered waste products of coal burning power plants and the issue ofhow to recycle or otherwise dispose of these products has become aconcern. While various methods have been attempted to recycle thesematerials, (such as using small amounts in concrete), the currentapplications using such ash are limited due to certain undesirableproperties of the ash. Thus, despite years of effort in searching forviable uses of the ash, substantial amounts of the ash go unused and aretransported to landfills. The amount of ash that must be transported andthen put into such landfills is significant.

The inventors herein have recognized a new approach using ash in roadstabilization that takes advantages of the properties of ash. In the newapproach, the ash may be used to stabilize various types of road bases,including dirt/gravel roads and sand roads. In tone example, a processfor the stabilization of roadways uses a combination of ash and anemulsion. One example process comprises mixing 5% to 50% of dry fly ashper square yard and 0.5 gallons to 2.5 gallons per square yard of theemulsion to the same area. The emulsion may be either of a resin base orasphalt base. However, various other ratios may be used, and additionalmaterials may be added to further improve the road stabilization.

In another example, a durable, stabilized road base is obtained using aprocess that uses the existing roadbed soils, tilling it to a depth ofapproximately 4-6 inches, blending in approximately 10-25% coalcombustion fly ash, introducing a site specific quantity of an emulsion,then grading and roller compacting the materials. The resultant roadbase may be significantly more stable and stronger than previous methodsof stabilizing the road base. Again, the road may be tilled to variousother depths, and various ratios of ash and an emulsion may be used.Further, various types of post processing may be used in place ofgrading an roller compacting, or these acts may not be used, if desired.

Thus, in at least some of the approaches herein, ash that wouldotherwise be transported to landfills may be beneficially used toimprove roadway construction. In some examples, the addition of ashprovides for strengthened road bases, while reducing the amount of othermore expensive materials that would otherwise be used to create the roadbase. Further, the ash can provide a stronger surface, withoutsubstantial disruption to the environment.

Various other examples are described herein.

Examples of dust suppressants and soil stabilizers are disclosed in U.S.Pat. Nos. 4,001,033; 4,571,116; 4,737,305; 4,801,635; 5,084,207;5,412,007; and 5,824,725, the disclosures of which are incorporated byreference in their entirety for all purposes.

In another aspect of the disclosure, the inventors herein have foundthat a mixture of ash, and emulsion, and optionally mixed with soil mayprovide termite deterrence.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example road surface; and

FIG. 2 shows an example mixture process.

DETAILED DESCRIPTION

As described above, in one example, a coal combustion product, such asash, may be combined with an emulsion and used in constructing a roadbase. The ash is a byproduct/waster product of burning coal. There arevarious types of ash that may be produced by coal-burning plants,including bottom ash, boiler slag, fly ash, and mixtures of such ashes.

In one specific example described in detail herein, fly ash may be usedwith an emulsion to provide an increased stabilized road surface, suchas shown in FIG. 1, which shows a road surface 110 including a road bedlayer 112 and a second layer 114 including at least ash and an emulsion(which may each be in layers within layer 114, or may be mixedtogether). Thus, fly ash may be optionally used with an emulsion toprevent erosion of banks or fields. The emulsion may operate to bind thefly ash and retain it in a form which creates a substantially durablehard surface. By mixing the emulsion and fly ash into the roadbed (alsoreferred to herein as the mixing surface), it may be possible tocost-effectively stabilize and improve the durability and lifeexpectancy of the road. The mixture may provide a “concrete-like” or“paved-type” surface.

Briefly, as described above, fly ash is a byproduct of the coal-burningprocess and is in the form of very fine coal particles. These very finecoal particles may be transported from the combustion chamber by exhaustgases. The fly ash is typically a fine powder-like substance formed fromthe mineral matter in some coal, including the noncombustible matter incoal plus a small amounts of carbon that remain from incompletecombustion.

In some embodiments, fly ash may comprise mostly silt-sized andclay-sized glassy spheres, with a consistency somewhat like talcumpowder. Properties of fly ash may vary with coal composition andplant-operating conditions. For example, the properties of fly ash mayvary on different operations within the coal plant, such as selection,carbon reduction, classification, grinding, blending and homogenization.

Further, fly ash can be characterized into different classes dependingon its characteristics. For example, ASTM C618 defines two classes offly ash: F and C. Any of the various types of ash, and specifically flyash, may be advantageously used in the present disclosure. Moreover, thevarious types of fly ash may be used depending on the type of surfacewhich the ash may be applied.

To determine if fly ash can be used as an ingredient in base materialfor roads, the following tests were performed. First, a type of fly ashwas selected from three types of available fly ash: ash from wood only,ash from coal only, and ash from coal with limestone added. While allthree types of ash can be effectively used to attain a cohesive mixture,ash from coal with limestone added was selected for testing because ofhardening qualities demonstrated by limestone.

Then, the following mixture results were obtained. Mixture A: Onehundred percent ash with 4:1 mixture of an emulsion (such as the onedescribed below) produces a cohesive mixture, however there may be lowstrength. Mixture B: 75% clay, 25% ash and a 4:1 mixture with anemulsion (such as the one described below) produces a cohesive mixture,with strength being higher than Mixture A. Mixture C: soil with highorganic content mixed at a rate of 75% soil, 25% ash and a 4:1 mixtureof an emulsion (such as the one described below herein) produces acohesive mixture with good strength (better strength than Mixture B).Mixture D: sand clay (as it normally exists in South Carolina and othersimilar geographical areas) mixed as a rate of up to 70% sand clay and30% ash provides a good mixture with good strength. As such, the highstrength and highly cohesive mixture may be attained with 15% ash, 85%sand clay and 4:1 emulsion (such as the one described below herein).Mixture E: pure sand or so called “sugar sand” mixed at rate of 85%sand, 15% ash with 4:1 emulsion (such as the one described below herein)also produces an extremely high strength and highly cohesive mixture.Mixture F: a limited test conducted with material such as crushed run.

It should be appreciated that the amount of ash and the amount ofemulsion may be varied depending on the type of soil or road surfacematerial. Moreover, the amount of emulsion may further be based on theamount of moisture in the soil and/or the fly ash. For example, variousclassifications of ash may be selected for use on a specific type ofsoil bed, e.g. sand, dirt/gravel. The amount of emulsion may depend onthe classification of the ash. Further, the amount of fly ash may bevaried depending on the road surface. For example, for a hard gravelsurface, as little as 5% fly ash may be used, while on a sand surface,as much as 50% fly ash may be used. Thus, fly ash may work well withaggregates provided a sufficient amount of ash is used to fill voidsaround aggregates.

As noted above, one example mixture comprises 5% to 50% of dry fly ashper square yard and 0.5 gallons to 2.5 gallons per square yard of theemulsion to the same area. The emulsion may be either of a resin base orasphalt base. However, various other ranges of dry fly ash per yard maybe used, such as 5-10%, 10-20%, 5-20%, 10-25%, 25-45%, 30-50%, 35-50%,45-50%, etc. Likewise, various other ranges of emulsion gallons persquare yard may be used, such as 0.5-1, 1-2, 1-1.5, 0.5-2, 0.5-1.5, etc.

As also noted above, a durable, stabilized road base may be obtainedusing a process such as that described in FIG. 2. In this example, theprocess uses the existing roadbed soils, tilling it to a depth ofapproximately 4-6 inches (step 310), blending in approximately 10-25%coal combustion fly ash (step 312), introducing a site specific quantityof an emulsion (step 314), then grading (step 316) and roller compacting(step 318) the road. Depending on the application and the soil material,various tilling depths may be used, such as 1-3 inches, 0.5-5 inches,5-10 inches, etc. Further, various blends of ash may be introduced, suchas 5-50%, 20-30%, 10-40%, 25-50%, 35-45%, etc. By varying the amount ofash, emulsion and tilled soil, the strength of the mixture and the mixedcomposition may be tailored to the specific needs of the roadway.

By using the fly ash with the emulsion, it may be possible tosubstantially improve the strength of the road base. By improving thestrength of the road base, the durability and life expectancy of roadsmay be improved. Further, use of the fly ash may substantially reducethe costs of stabilizing roadways. As a waste product, the cost of flyash is minimal relative to other materials used to stabilize roadways.With such large amounts of the waste product available, thisadvantageous use of the material enables substantial recycling of apreviously hard-to-dispose product.

Also, while the above ranges show exact percentages, there may be somevariation in the actual percentage, including 0-10% variation, forexample, and as such these ranges may be approximate.

Testing was also done to study if and how an emulsion (such as the onedescribed below) mixed with existing soil and fly ash may affecttermites. The soil condition of the subject test soil was heavy claywith a small amount of fine native stone, mostly quartz. The test areawas heavily wooded with obvious presence of termite colonies. Thematerial formulation used included: 4 parts native soil taken from atermite infested area, 1 part fly ash from a South Carolina coal plant,added with a sufficient amount of a 50% emulsion to create a mixtureconsistent with flowable concrete.

The above material was applied to an excavated area 18″ long, 12″ wideand 4″ deep. It was mixed as noted above and placed in the excavatedarea, along with a 2″ section of new white pine 2 ×4 on top, leavingarea exposed to elements. Over the testing period, where results wereconsistently checked termites were absent from the treated material.Specifically, the test was run for several months, where at time 1 (noevidence of termites); time 2 (two months later) (no evidence oftermites); and six months following time 2 (still free of termites).

While the above mixture therefore provides significant termiteprotection, various other combinations may also be used. For example,the ratio of fly ash to soil may be varied depending on soil moistureand soil type.

Various types of emulsions may be used in the above-disclosed mixtureswith the fly ash. Specifically, any suitable resin-based material may beused in the mixture. For example, resin materials having a cast numberof 64742-16-1; 64742-11-6; and asphalt 8502-42-4 would be suitableemulsion products.

As an exemplary emulsion, and not as a limitation, one product which maybe mixed with the fly ash as the emulsion is EARTHBIND® 100. An exampleof such a product is described in TABLE A, and is included only forillustrative purposes. It should be appreciated that although anexemplary composition is described in detail, the components and theweight percent of the components within the composition may vary.

One example composition of the emulsion includes a polymeric liquid orresin. Typically, the resin will be a petroleum resin in amounts ofapproximately 20 wt. % to 80 wt. %. An exemplary composition may include40 wt. % to 60 wt. % of a petroleum resin as shown in TABLE A. TABLE AComponent Range (wt. %) Exemplary Composition (wt. %) Petroleum resin20-80 40-60 Lignin sulfonate 10-60 15-45 of an lignin sulfonateSurfactant  1-20 6-8 Water  0-95  0-95

Petroleum resins, as used in the composition, may function to bind oradhere to surfaces having various types of soil particles, includingsand, gravel and dirt. The petroleum resins may further bind to productssuch as the fly ash. The petroleum resins may be adapted to bind suchparticles together for extended periods of time. After application andadherence to a surface, the petroleum resins function as awater-proofing membrane, repelling water off the surface. Although avariety of petroleum resins may be used, petroleum resins having aviscosity in the range of approximately 3000 to 5000 SUS at 210° F.enables the petroleum resin within the composition to develop asubstantial film thickness, or mat, over the soil particles uponapplication. The substantial film provides an increased binding powerfor the soil particles. The depth of the film further prevents thecomposition from becoming air borne once it is broken away from thesurface of the mat.

As shown in the above table, the composition may optionally also includea stabilizer, such as a liquid lignin sulfonate. Lignin sulfonate, asused herein, is a metallic sulfonate salt made from the lignin ofsulfite pulp-mill liquors. Such lignin sulfonate is approximately 20 wt.% to 60 wt. % of the overall composition. Lignin sulfonate may act as awatering agent and as a soil stabilizer to bind to various types ofsoils and ash. The combination of the petroleum resin and the ligninsulfonate result in a composition that is adapted to provide effectivelybinding of various types of soils particles and/or ash together.Further, it may also generate a substantially waterproof surface. Thisbinding may further function to mitigate airborne particles and preventthe fly ash from dispersing over time from roadway use.

It should be appreciated that various types of lignin sulfonates may beused. For example, both ammonium lignin sulfonate and/or a calciumlignin sulfonate are suitable lignin sulfonates. It should beappreciated that other types of lignin sulfonates may be used,including, but not limited to sodium lignin sulfonate. The type oflignin sulfonate used may depend on the specific application of thecomposition. Thus, in the exemplary composition, ammonium ligninsulfonate is identified as a suitable lignin sulfonate, however itshould be appreciated that for other road surfaces or conditions adifferent lignin sulfonate may be used. The ammonium lignin sulfonate ofthe exemplary composition is shown as being generally 15 wt. % to 45 wt.% of the composition.

In addition to the petroleum resin and the lignin sulfonate, thecomposition further may include approximately 1 wt. % to 20 wt. % of asurfactant, also referred to herein as the emulsifier. As shown in TableA, in the exemplary composition, the surfactant may be only 6 wt. % to 8wt. % of the composition.

The surfactant in the composition may optionally be a non-ionicsurfactant. For example, alkylphenols, such as a nonylphenol(C₉H₁₉C₆H₄OH), may be used as the non-ionic surfactant. The presentsurfactant functions as an emulsifier which is adapted to wet outvarious types of soil surfaces (regardless of charge). Unlike anoppositely-charged surfactant system, which is configured to wet only aspecific surface type, the present emulsifier may be adapted to wet avariety of surfaces making the overall composition extremely versatile.

In an oppositely-charged surfactant system, the type of particles and/orsoil may require use of a different charged emulsifier. For example,with limestone aggregates (having a positive charge on the surface), anegatively-charged emulsifier (anionic) may be required to get the bestwetting of the particles. Similarly, a granite surface (having anegative charge on the surface), would require a positively-chargedemulsifier (cationic) to get the best wetting of the particles. In thepresent composition, the non-ionic emulsifier enables maximum wetting ofthe different types of particles, such as soil. Thus, the non-ionicemulsifier is adapted to wet out both cationic and anionic soils (e.g.,limestone and granite, respectively) quickly and more efficiently thanusing an oppositely-charged surfactant system. It should be appreciatedthat the wetting of the soil enables the petroleum resin to come intocloser contact with individual particles. The ability to come intocloser contact may result in more thoroughly coated particles, creatinga more weatherproof surface once compacted.

Another consideration regarding the emulsifier is the overall stabilityof the emulsifier. A good emulsifier for the present composition is astable product that is easily useable in the field. Further, theemulsifier should be easy to store and transport, such that there are nodifficulties in transporting or handling the composition or itscomponents.

The petroleum resin, lignin sulfonate and emulsifier may be mixed in anysuitable manner. For example, in some embodiments, the materials may bemixed with a blender or other mixing device. In other embodiments, thematerials may be combined using an emulsion mill. For example, thecomponents described above may be ground together using an emulsionprocess to form an emulsion. The manufacturing of a standard emulsionmay be accomplished by adding enough shear force to a product to grindthe product into small droplets. The small droplets may then besuspended in the composition. In the present disclosure, the mechanicalprocess of grinding the components together to form an emulsion may beaccomplished using a colloid mill or other similar device.

Thus, emulsion of the components may be controlled by use of the colloidmill. By controlling temperature and flow rates, the emulsion processmay be controlled to optimize the particle size for emulsion stabilityand performance of the composition in the field. The optimal particlesize may vary depending on the intended application of the product.Typically, the smaller the particle size the better the emulsion.

Upon application to a surface, the emulsion composition is adapted topenetrate the surface, as well as the fly ash. Specifically, thesurfactantlemulsifier, when added to water, operates as a wetting agentallowing the composition to penetrate into, or to spread over, the roadsurface by reducing the surface tension of the water. As describedabove, the amount of each of the components may vary on the specificintended application, such as the type of surface to be treated.Moreover, the amount of water may vary. Thus, the composition mayinclude anywhere from approximately 0 wt. % to 95 wt. % water.

It should be appreciated that the emulsion product may be stored in aconcentrated form and diluted prior to application. For example, theproduct may be used at water-to-product concentrations of 3:1 to 20:1depending on the soil type, traffic flow, amount of ash and otherenvironmental factors.

The ranges provided for the petroleum resin, the lignin sulfonate, andthe emulsifier are preferred ranges that enable the composition to workwith a large number of different types of aggregate roadways and othersuitable surfaces for soil stabilization. Although, described in termsof the optimal ranges, it should be noted that the ranges may varydepending on the field conditions, such as the type and amount ofaggregate. Thus, the composition may vary where the aggregate includes alarge amount of fine particulates. For example, in some fieldconditions, the petroleum resin, may optimally range from 1 wt. % to 70wt. %. Similarly, for those same field conditions, the lignin sulfonatemay range from 0.5 wt. % to 25 wt. %, while the surfactant may rangefrom 0.2 wt. % to 15 wt. %. Similarly, water, being the carrier solvent,may range between 60 wt. % to 95 wt. %.

The texture of the soil or other particulates may affect the proportionof petroleum resin to lignin sulfonate in the emulsion composition. Forexample, coarse soil (such as sandy regions) may require a higherproportion of petroleum resin to lignin sulfonate. The larger amount ofpetroleum resin may prevent the lignin sulfonate from penetrating thesurface too quickly. In contrast, finer particles may require morelignin sulfonate, and thus, may have a lower proportion of petroleumresin to lignin sulfonate in the overall emulsion composition comparedto an emulsion composition for coarse particles.

It should be noted that none of components in the present composition,including both the emulsion and the fly ash, are listed as hazardous ortoxic materials. The composition may be safe to apply and use and mayhave little or no detrimental effect on the environment.

It is believed that the disclosure set forth above encompasses multipledistinct inventions with independent utility. While each of theseinventions has been disclosed in its preferred form, the specificembodiments thereof as disclosed and illustrated herein are not to beconsidered in a limiting sense as numerous variations are possible. Thesubject matter of the inventions includes all novel and non-obviouscombinations and subcombinations of the various elements, features,functions and/or properties disclosed herein. Similarly, where theclaims recite “a” or “a first” element or the equivalent thereof, suchclaims should be understood to include incorporation of one or more suchelements, neither requiring, nor excluding, two or more such elements.

Inventions embodied in various combinations and subcombinations offeatures, functions, elements, and/or properties may be claimed in arelated application. Such claims, whether they are directed to adifferent invention or directed to the same invention, whetherdifferent, broader, narrower or equal in scope to any original claims,are also regarded as included within the subject matter of theinventions of the present disclosure.

1. A mixture, comprising: fly ash; and an emulsion, where said emulsionis mixed with said fly ash in a range of 5% to 50% of fly ash per anarea of a square yard and 0.5 gallons to 2.5 gallons per square yard ofthe emulsion to said area.
 2. The mixture of claim 1 wherein saidmixture is applied as a layer of a stabilized road base.
 3. The mixtureof claim 2 wherein said emulsion is of a resin base;
 4. The mixture ofclaim 2 wherein said emulsion is of an asphalt base.
 5. The mixture ofclaim 2 wherein said road based includes at least one of dirt, gravel,and sand roads, and wherein said fly ash includes limestone.
 6. Themixture of claim 5 wherein said fly ash includes dry fly ash.
 7. Themixture of claim 5 wherein said fly ash includes coal ash.
 8. Themixture of claim 5 wherein said fly ash includes bottom ash.
 9. Astabilized road base, comprising: a first layer comprising ash and anemulsion; and a second layer comprising a roadbed.
 10. The road base ofclaim 9 wherein said first layer is a mixture of at least said ash andsaid emulsion, and said ash includes ash from coal with limestone. 11.The road based of claim 9 wherein said first layer includes an ash layerand an emulsion layer.
 12. The road based of claim 10 wherein said ashincludes fly ash.
 13. The road based of claim 12 where said roadbed is atilled roadbed that has been tilled to a depth of at least 4 inches. 14.The roadbed of claim 13 wherein said first layer is over second layer.15. The roadbed of claim 14 wherein said emulsion includes a resin base.16. The roadbed of claim 14 wherein said emulsion includes an asphaltbase.
 17. A process for stabilizing a road base, comprising: tilling aroadbed soil; blending in ash; introducing a site specific quantity ofan emulsion; and grading and roller compacting said road bases.
 18. Theprocess of claim 17 where said roadbed soil is tilled to a depth ofapproximately 4-6 inches.
 19. The process of claim 17 whereinapproximately 10-25% coal combustion fly ash is blended into saidroadbed soil, and said ash including ash from coal with limestone. 20.The process of claim 19 wherein said roadbed soil is an existing roadbedsoil.
 21. A process for stabilizing a road, comprising: mixing 5% to 50%of dry fly ash per square yard and an of the emulsion to the same area;and applying said mixture to the road.
 22. The process of claim 21wherein said road includes one of a dirt, gravel, or sand road, and saidash including ash from coal with limestone.
 23. A mixture for deterringinsects, the mixture comprising: ash; and an emulsion.
 24. The mixtureof claim 23, where said ash includes fly ash, wherein a ratio of saidmixture is formed with one part fly ash with a sufficient amount of a50% emulsion to create a mixture consistent with flowable concrete.